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Abstract:

A lithography apparatus includes a stage on which a target object is
placed; a chamber in which the stage is arranged and which has one side
surface in which an opening having a size which is enough to carry the
stage in or out is formed, the opening being closed with an independent
lid; an electro-optic lens barrel arranged on the chamber; and a rib
portion formed to have a shape that is convex on an upper portion of the
side surface of the chamber in which the opening is formed.

Claims:

1. A lithography apparatus comprising:a stage on which a target object is
placed;a chamber in which the stage is arranged and which has one side
surface in which an opening having a size which is enough to carry the
stage in or out is formed, the opening being closed with an independent
lid;an electro-optic lens barrel arranged on the chamber; anda rib
portion formed to have a shape that is convex on an upper portion of the
side surface of the chamber in which the opening is formed.

2. The apparatus according to claim 1, wherein the rib portion is formed
to have a shape that is upwardly convex and extending from an upper
surface of the chamber.

3. The apparatus according to claim 1, wherein the rib portion is formed
to have a convex shape in a direction parallel to an upper surface of the
chamber.

4. The apparatus according to claim 1, wherein the rib portion is formed
to have a shape that is upwardly convex extending from an upper surface
of the chamber and that is convex in a direction parallel to the upper
surface of the chamber.

5. The apparatus according to claim 1, wherein the rib portion is formed
integrally with the chamber.

6. The apparatus according to claim 5, wherein the rib portion is arranged
at a position not to be in contact with the electro-optic lens barrel.

7. The apparatus according to claim 6, wherein the rib portion is made of
a plate-like member.

8. The apparatus according to claim 1, whereinthe chamber has a plurality
of side surfaces, anda rigidity of the side surface in which the rib
portion is formed is made equal to that of an opposite side surface in
which the rib portion is not formed.

9. A lithography method comprising:controlling to be a vacuum state in a
chamber having a side surface in which an opening is formed, the side
surface being reinforced by a rib portion, and an electro-optic lens
barrel arranged on the chamber; andirradiating a charged particle beam
from the electro-optic lens barrel to a target object placed on a stage
arranged in the chamber in the vacuum state to form a pattern.

10. The method according to claim 9, further comprisingreinforcing the
side surface by using the rib portion such that an amount of deformation
of the side surface in which the opening is formed is equal to that of an
opposite side surface in which the opening is not formed in the vacuum
state.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

[0001]This application is based upon and claims the benefit of priority
from prior Japanese Patent Application No. 2009-065599 filed on Mar. 18,
2009 in Japan, the entire contents of which are incorporated herein by
reference.

BACKGROUND OF THE INVENTION

[0002]1. Field of the Invention

[0003]The present invention relates to a lithography apparatus and a
lithography method and, in particular, to a lithography apparatus and a
lithography method for forming patterns by using electron beams in a
vacuum state.

[0004]2. Related Art

[0005]A photolithography technique which takes a part of the development
of miniaturization of semiconductor devices is only a process, in which a
pattern is generated, in semiconductor manufacturing processes and is
very important. In recent years, with the advancement in integration
density of an LSI, circuit line widths required for semiconductor devices
are miniaturized year by year. In order to form desired circuit patterns
on the semiconductor devices, precise original patterns (to be also
referred to as a reticle or a mask) are required. In this case, an
electron beam writing technique has an essentially excellent resolution,
and is used in production of precise original patterns.

[0006]FIG. 10 is a conceptual diagram for explaining an operation of a
variable-shaped electron beam lithography apparatus. The variable-shaped
electron beam lithography apparatus operates as follows. An oblong, for
example, rectangular opening 411 to shape an electron beam 330 is formed
in a first aperture plate 410. A variable-shaped opening 421 to shape the
electron beam 330 having passed through the opening 411 of the first
aperture plate 410 into a desired oblong shape is formed in a second
aperture plate 420. The electron beam 330 irradiated from the charged
particle source 430 and having passed through the opening 411 of the
first aperture plate 410 is deflected by a deflector, passes through a
part of the variable-shaped opening 421 of the second aperture plate 420,
and is irradiated on a target object 340 placed on a stage continuously
moving in one predetermined direction (for example, an X direction). More
specifically, an oblong shape which can pass through both the opening 411
of the first aperture plate 410 and the variable-shaped opening 421 of
the second aperture plate 420 is written in a write region of the target
object 340 placed on the stage continuously moving in the X direction. A
scheme which causes an electron beam to pass through both the opening 411
of the first aperture plate 410 and the variable-shaped opening 421 of
the second aperture plate 420 to form an arbitrary shape is a
variable-shaping scheme.

[0007]FIG. 11 is a conceptual diagram showing a housing configuration of
the lithography apparatus. In FIG. 11, in the electron beam lithography
apparatus, a stage 305 on which a target object 301 is placed is
accommodated in a write chamber 303. On the write chamber 303, an
electro-optic lens barrel 302 on which the electro-optic system described
above is mounted is arranged. In a writing operation, the electro-optic
lens barrel 302 and the write chamber 303 are vacuumed by a vacuum pump
310, and a pattern is formed on the target object 301 in vacuum. In this
case, in order to install, remove, or check the stage 305 in the write
chamber 303, an opening 320 having a size which is enough to carry the
stage 305 in or out. While the electro-optic lens barrel 302 and the
write chamber 303 are vacuumed, the opening 320 is closed by a door 331.
The door 331 can be opened and closed, and is fixed to a side surface
with a screw or the like.

[0008]In this case, when the inside and outside of the write chamber 303
are in an atmospheric pressure, any problem is not posed. However, since
a pressure difference occurs in the inside and outside of the write
chamber 303 when the write chamber 303 is set in a vacuum state, a
circumferential surface of the write chamber 303 is deformed. At this
time, since the rigidity of a side surface in which the opening 320 is
formed and the rigidity of a side surface in which the opening 320 is not
formed are different from each other, amounts of deformation are
different from each other to tilt the electro-optic lens barrel 302 to a
side of the low-rigidity side surface in which the opening 320 is formed.
When the electro-optic lens barrel 302 is tilted, the trace of an
electron beam is misaligned to disadvantageously cause an error in size
of a pattern to be formed. In particular, an amount of deformation of the
write chamber 303 changes depending on a variation in atmosphere. For
this reason, an angle θ at which the electro-optic lens barrel 302
is tilted changes depending on a variation in atmosphere, and an error of
a write position changes accordingly. In particular, a higher
pattern-forming accuracy is required with miniaturization of a circuit
line width in recent years, and thus deterioration in pattern-forming
accuracy caused by positional misalignment by a variation in atmosphere
is not negligible. In a conventionally, this problem is addressed by
correcting a deflection position of an electron beam. However, this
correction cannot be easily performed when an amount of deformation
becomes large.

[0009]A technique (for example, see Japanese Unexamined Patent Publication
No. 7-211612) which calculates an amount of field distortion caused by a
variation in atmosphere by a projection optical system which exposes a
mask image on a wafer to move a stage to an appropriate position is
disclosed in a document.

[0010]As described above, the angle by which the electro-optic lens barrel
is tilted on the weak side surface side on which the opening is formed
changes depending on a variation in atmosphere, and an error in size of a
pattern to be formed occurs disadvantageously. For this reason, a small
tilt angle is desired, however, a measure for the small tilt angle has
not been made.

BRIEF SUMMARY OF THE INVENTION

[0011]It is an object of an embodiment of the present invention to provide
a lithography apparatus and a lithography method which can make a tilt
angle of an electro-optic lens barrel used in a vacuum state smaller.

[0012]In accordance with one aspect of the present invention, a
lithography apparatus includes a stage on which a target object is
placed; a chamber in which the stage is arranged and which has one side
surface in which an opening having a size which is enough to carry the
stage in or out is formed, the opening being closed with an independent
lid; an electro-optic lens barrel arranged on the chamber; and a rib
portion formed to have a shape that is convex on an upper portion of the
side surface of the chamber in which the opening is formed.

[0013]In accordance with another aspect of the present invention, a
lithography method includes controlling to be a vacuum state in a chamber
having a side surface in which an opening is formed, the side surface
being reinforced by a rib portion, and an electro-optic lens barrel
arranged on the chamber; and irradiating a charged particle beam from the
electro-optic lens barrel to a target object placed on a stage arranged
in the chamber in the vacuum state to form a pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a conceptual diagram showing a configuration of a
lithography apparatus according to Embodiment 1.

[0015]FIG. 2 is an appearance diagram of the lithography apparatus
according to Embodiment 1.

[0016]FIG. 3 is a conceptual diagram showing a section of a writing
chamber according to Embodiment 1.

[0017]FIG. 4 is a diagram showing an example of an appearance of the
lithography apparatus according to Embodiment 1.

[0018]FIG. 5 is a diagram showing another example of the appearance of the
lithography apparatus according to Embodiment 1.

[0019]FIG. 6 is a diagram showing an example of the lithography apparatus
according to Embodiment 1.

[0020]FIG. 7 is a diagram showing an example of the lithography apparatus
according to Embodiment 1.

[0021]FIG. 8 is a diagram showing an example of the lithography apparatus
according to Embodiment 1.

[0022]FIG. 9 is a conceptual diagram for explaining a state in which the
writing chamber according to Embodiment 1 is vacuumed.

[0023]FIG. 10 is a conceptual diagram for explaining an operation of a
variable-shaped exposure device.

[0024]FIG. 11 is a conceptual diagram for explaining a housing
configuration of the lithography apparatus.

DETAILED DESCRIPTION OF THE INVENTION

Embodiment 1

[0025]In an embodiment, a configuration using an electron beam as an
example of a charged particle beam will be described below. The charged
particle beam is not limited to an electron beam, and a beam such as an
ion beam using charged particles may be used.

[0026]FIG. 1 is a conceptual diagram showing a configuration of a
lithography apparatus according to Embodiment 1. In FIG. 1, a lithography
apparatus 100 includes a write unit 150 and a control circuit 160. The
lithography apparatus 100 forms a pattern on a target object 101 on which
a resist is coated by using an electron beam 200. The write unit 150 has
an electro-optic lens barrel 102 and a writing chamber 103. The
electro-optic lens barrel 102 is arranged on the writing chamber 103.

[0027]In the electro-optic lens barrel 102, an electron gun assembly 201,
an illumination lens 202, a first aperture plate 203, a projection lens
204, a deflector 205, a second aperture plate 206, an objective lens 207,
and a deflector 208. In the writing chamber 103, an X-Y stage 105 is
arranged. On the X-Y stage 105, the target object 101 serving as an
object on which a pattern is to be formed is placed. The target object
101 includes a mask substrate, a wafer, or the like.

[0028]The write unit 150 is controlled by the control circuit 160. In a
wiring operation, the electro-optic lens barrel 102 and the writing
chamber 103 are controlled to be a vacuum state by exhausting in the
electro-optic lens barrel 102 and the writing chamber 103 by a vacuum
pump 170. In order to install, remove, or check the X-Y stage 105 in the
writing chamber 103, an opening 20 having a size which is enough to carry
the X-Y stage 105 in or out is formed in one side surface of the writing
chamber 103. While the writing chamber 103 is vacuumed, the opening 20 is
closed with a door 30 that is an independent lid. The door 30 can be
opened and closed and is fixed to the side surface with a screw or the
like.

[0029]FIG. 2 is an appearance diagram of the lithography apparatus
according to Embodiment 1. On one surface of the circumferential surfaces
of the writing chamber 103, as described above, the opening 20 having a
size which is enough to carry the X-Y stage 105 in or out is formed. For
this reason, in this state, the rigidity or "hardness" of a side surface
40 in which the opening 20 is formed is lower than that of a side surface
in which the opening 20 is not formed. Therefore, in Embodiment 1, a rib
portion 10 formed to have a convex shape is formed on an upper part of
the side surface 40 of the writing chamber 103 in which the opening 20 is
formed. The circumferential surfaces of the writing chamber 103, for
example, are integrally formed by fixing plate-like members by welding.
The rib portion 10 is formed integrally with the writing chamber 103.
When an upper part of the side surface of the writing chamber 103 in
which the opening 20 is formed is reinforced by the rib portion 10, the
rigidity of the side surface of the writing chamber 103 in which the
opening 20 is formed can be improved. The size of the rib portion 10 is
arbitrarily adjusted to make it possible to make the rigidity of the side
surface of the writing chamber 103 in which the opening 20 is formed
equal to or closer to the rigidity of the side surface of the writing
chamber 103 in which the opening 20 is not formed. The rib portion 10 is
preferably formed to have the same width as that of the side surface 40
of the writing chamber 103 in which the opening 20 is formed.

[0030]FIG. 3 is a conceptual diagram showing a section of the writing
chamber according to Embodiment 1. As shown in FIG. 3, the rib portion 10
is preferably formed to have an upwardly convex shape or a horizontally
convex shape. An example of the rib shape will be illustrated below.

[0031]FIG. 4 is a diagram showing an example of an appearance of the
lithography apparatus according to Embodiment 1. FIG. 4 shows a case in
which a rib portion 12 is formed to have a shape that is upwardly convex
extending from the upper surface of the writing chamber 103. In FIG. 4,
for example, a plate to be used as the side surface of the writing
chamber 103 in which the opening 20 is formed is welded to upwardly
project from the upper plate of the writing chamber 103.

[0032]FIG. 5 is a diagram showing another example of the appearance of the
lithography apparatus according to Embodiment 1. FIG. 5 shows a case in
which a rib portion 14 is formed to have a shape that is convex in a
direction parallel to the upper surface of the writing chamber 103. In
FIG. 5, for example, a plate to be used as the upper surface of the
writing chamber 103 is welded to project from the side surface plate of
the writing chamber 103 in which the opening 20 is formed to a side
surface side to make it possible to form the rib portion 14.

[0033]FIG. 6 is a diagram showing an example of the appearance of the
lithography apparatus according to Embodiment 1. FIG. 6 shows an example
in which a rib portion 16 is formed to have a shape that is upwardly
convex extending from the upper surface of the writing chamber 103 and
that is convex in a direction parallel to the upper surface of the
writing chamber 103. In FIG. 6, a case in which the thickness of the rib
portion 16 is increased toward the inside of the writing chamber 103 as
the direction parallel to the upper surface of the writing chamber 103 is
shown.

[0034]FIG. 7 is a diagram showing an example of the appearance of the
lithography apparatus according to Embodiment 1. FIG. 7 shows another
example in which a rib portion 18 is formed to have a shape that is
upwardly convex extending from the upper surface of the writing chamber
103 and that is convex in a direction parallel to the upper surface of
the writing chamber 103. In FIG. 7, a case in which the rib portion 16 is
extended toward the outside of the writing chamber 103 as the direction
parallel to the upper surface of the writing chamber 103 is shown.

[0035]FIG. 8 is a diagram showing an example of the lithography apparatus
according to Embodiment 1. FIG. 8 shows another example in which a rib
portion 19 is formed to have a shape that is upwardly convex extending
from the upper surface of the writing chamber 103 and that is convex in a
direction parallel to the upper surface of the writing chamber 103. In
FIG. 8, a case in which the rib portion 16 is extended toward both the
outside and the inside of the writing chamber 103 as the direction
parallel to the upper surface of the writing chamber 103 is shown.

[0036]By forming the rib portion in any of the shapes described above, the
rigidity of the side surface of the writing chamber 103 in which the
opening 20 is formed can be improved.

[0037]FIG. 9 is a conceptual diagram for explaining a state in which the
writing chamber according to Embodiment 1 is vacuumed. As described
above, the rib portion 10 is integrally formed on the upper portion of
the side surface of the writing chamber 103 in which the opening 20 is
formed. In this manner, when the electro-optic lens barrel 102 and the
writing chamber 103 are vacuumed with the vacuum pump 170, an amount of
deformation of the side surface of the writing chamber 103 in which the
opening 20 is formed can be made equal to or closer to an amount of
deformation of the side surface of the writing chamber 103 in which the
opening 20 is not formed in the vacuum state. As a result, amounts of
deformation of both the side surfaces are balanced, and thus a tilt angle
θ of the electro-optic lens barrel 102 can be reduced.

[0038]For example, in a conventional configuration in which a rib is not
formed, a beam displacement of 25 nm is observed when a variation in
atmosphere is 10 hPa. However, for example, in the example of the
configuration shown in FIG. 4, the beam displacement can be suppressed to
15 nm. The size of the rib portion 10 is arbitrarily adjusted to make it
possible to better balance the rigidities and to approximate the tilt
angle θ of the electro-optic lens barrel 102 to 0. Furthermore,
even when a variation in atmosphere occurs, a variation of the tilt angle
θ of the electro-optic lens barrel 102 can be reduced. As a result,
an error of a position of a beam irradiated on the target object 101 can
be reduced, and thus writing accuracy can be improved.

[0039]After the writing chamber 103 reinforced by the rib portion 10 as
described above and the electro-optic lens barrel 102 are controlled to
be a vacuum state by exhausting in the electro-optic lens barrel 102 and
the writing chamber 103, a writing operation is started in the vacuum
state. A concrete operation will be explained below.

[0040]The electron beam 200 emitted from the electron gun assembly 201
illuminates the entire first aperture plate 203 having an oblong, for
example, a rectangular hole by the illumination lens 202. In this case,
the electron beam 200 is firstly shaped into an oblong, for example, a
rectangle. The electron beam 200 of the first aperture plate image having
passed through the first aperture plate 203 is projected on the second
aperture plate 206 by the projection lens 204. A position of the first
aperture plate image on the second aperture plate 206 is controlled by
the deflector 205 so that a beam shape and a beam size can be changed.
The electron beam 200 of the second aperture plate image having passed
through the second aperture plate 206 is focused by the objective lens
207, deflected by the deflector 208, and irradiated on a desired position
of the target object 101 on the X-Y stage 105 which can be movably
arranged.

[0041]The embodiment has been described with reference to the concrete
examples. However, the present invention is not limited to the concrete
example.

[0042]Although parts such as an apparatus configuration and a control
method which are not directly required for the explanation of the present
invention are not described, a required apparatus configuration or a
required control method can be arbitrarily selected and used. For
example, although a configuration of a control unit which controls the
lithography apparatus 100 is not described, a required control unit
configuration can be arbitrarily selected and used as a matter of course.

[0043]All lithography apparatuses and position measuring methods which
include the elements of the present invention and can be arbitrarily
changed in design by a person skilled in the art are included in the
spirit and scope of the invention.

[0044]Additional advantages and modification will readily occur to those
skilled in the art. Therefore, the invention in its broader aspects is
not limited to the specific details and representative embodiments shown
and described herein. Accordingly, various modifications may be made
without departing from the spirit or scope of the general inventive
concept as defined by the appended claims and their equivalents.